Abstract: An improved gate valve for effective sealing regardless of the pressure of the fluid of the conduit to which the valve is attached. The gate valve comprises a body (20) having opposing upstream and downstream sides (46, 44). Each side has a conduit-joining surface (72, 73) formed thereon. The body is configured for connection between two axially aligned conduits (24, 25) with each conduit-joining surface abutted against the end of an associated conduit. A resilient liner (27) is attached to the body between the valve gate (32) and the body (20). The liner also covers the portion of the body that defines the port. The liner includes a sealing surface (60) formed thereon. The sealing surface is configured for sealing contact with the portion of the edge surface of the gate that resides within the body when the gate is in the closed position. The gate valve also includes at least one seal ring (62) positioned against the body at the periphery of the port on one side of the gate.

Abstract: A knife gate valve comprises a body member to which two aligned conduits are attached. The body member has a U-shaped internal recess of predetermined length formed within it. A removable sealing member fits within the recess and extends along its entire length. The sealing member includes a bearing portion and a resilient backing portion that are positioned face-to-face to each other. The bearing portion comprises a flexible plastic-type material having a self-lubricating, semi-hard surface that contacts the blade portion of the gate as it slides along the length of the recess to close the valve. The resilient backing member comprises an elastomer strip that contacts the bearing portion surface that is opposite to the blade portion contacting surface. The resilient backing portion yields to the pressure exerted by the gate as it closes, thereby to provide a tight seal for the valve.